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Chapter Introduction
NAG Toolbox

# NAG Toolbox: nag_sort_permute_check (m01zb)

## Purpose

nag_sort_permute_check (m01zb) checks the validity of a permutation.

## Syntax

[iperm, ifail] = m01zb(iperm, m1, 'm2', m2)
[iperm, ifail] = nag_sort_permute_check(iperm, m1, 'm2', m2)

## Description

nag_sort_permute_check (m01zb) can be used to check the validity of user-supplied ranks or indices, without the ranks or indices being corrupted.

None.

## Parameters

### Compulsory Input Parameters

1:     iperm(m2) – int64int32nag_int array
m2, the dimension of the array, must satisfy the constraint 0 < m1m2$0<{\mathbf{m1}}\le {\mathbf{m2}}$.
Elements m1 to m2 of iperm must be set to values which are supposed to be a permutation of the integers m1 to m2. If they are a valid permutation, the function exits with ${\mathbf{ifail}}={\mathbf{0}}$.
2:     m1 – int64int32nag_int scalar
The range of elements used in the array iperm and the range of values in the permutation, as specified under iperm.
Constraint: 0 < m1m2$0<{\mathbf{m1}}\le {\mathbf{m2}}$.

### Optional Input Parameters

1:     m2 – int64int32nag_int scalar
Default: The dimension of the array iperm.
The range of elements used in the array iperm and the range of values in the permutation, as specified under iperm.
Constraint: 0 < m1m2$0<{\mathbf{m1}}\le {\mathbf{m2}}$.

None.

### Output Parameters

1:     iperm(m2) – int64int32nag_int array
Used as internal workpsace prior to being restored and hence is unchanged.
2:     ifail – int64int32nag_int scalar
${\mathrm{ifail}}={\mathbf{0}}$ unless the function detects an error (see [Error Indicators and Warnings]).

## Error Indicators and Warnings

Errors or warnings detected by the function:
ifail = 1${\mathbf{ifail}}=1$
 On entry, m2 < 1${\mathbf{m2}}<1$, or m1 < 1${\mathbf{m1}}<1$, or m1 > m2${\mathbf{m1}}>{\mathbf{m2}}$.
ifail = 2${\mathbf{ifail}}=2$
Elements m1 to m2 of iperm contain a value outside the range m1 to m2.
ifail = 3${\mathbf{ifail}}=3$
Elements m1 to m2 of iperm contain a repeated value.
If ${\mathbf{ifail}}={\mathbf{2}}$ or 3${\mathbf{3}}$, elements m1 to m2 of iperm do not contain a permutation of the integers m1 to m2.

Not applicable.

None.

## Example

```function nag_sort_permute_check_example
iperm = [int64(7);6;10;2;8;12;3;4;11;5;1;9];
m1 = int64(1);
[ipermOut, ifail] = nag_sort_permute_check(iperm, m1)
```
```

ipermOut =

7
6
10
2
8
12
3
4
11
5
1
9

ifail =

0

```
```function m01zb_example
iperm = [int64(7);6;10;2;8;12;3;4;11;5;1;9];
m1 = int64(1);
[ipermOut, ifail] = m01zb(iperm, m1)
```
```

ipermOut =

7
6
10
2
8
12
3
4
11
5
1
9

ifail =

0

```